At last, for the joint precoding framework, we set the weights of users as \(\eta _{k}=1\) , and we assume that the csi is perfectly knownIn this paper, the CSI is assumed to be perfectly known, while the challenging problem of channel estimation [1]} is left for future work.. As an alternating algorithm, \(\mathbf {\Theta }\)  is initialized by random values in \({\cal F}\) , and \(\bf W\)  is initialized by identical power and random phases.
